#include<bits/stdc++.h>
using namespace std;
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};
int Q[105][105],n,MAX=0,MIN=99999999;
int ans=99999999;
bool panduan(int x,int y)
{
	if(x<=0||y<=0||x>n||y>n) 
		return false;
	else 
		return true;
}
bool vis[105][105];
bool dfs(int x,int y,int l,int r)
{
	if(Q[x][y]<l||Q[x][y]>r) return false;
	if(x==n&&y==n) return true;
	vis[x][y]=1;
	for(int i=0;i<4;i++)
	{
		int nx=x+dx[i];
		int ny=y+dy[i];
		if(!panduan(nx,ny)||vis[nx][ny]) 
			{
				continue;
		}
		if(dfs(nx,ny,l,r)) 
			{
				return 1;
		}
	}
	return 0;
}
void WORK()
{
	for(int i=MIN;i<=MAX;i++)
	{
		for(int j=i;j<=MAX;j++)
		{
			if(j-i>=ans) continue;
			memset(vis,0,sizeof(vis));
			if(dfs(1,1,i,j)) 
				{
					ans=j-i;
			}
			
		}
	}
	cout<<ans;
}
int main()
{
	ios::sync_with_stdio(false);
	freopen("adven.in","r",stdin);
	freopen("adven.out","w",stdout);
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=n;j++)
		{
			cin>>Q[i][j];
			MIN=min(Q[i][j],MIN);
			MAX=max(Q[i][j],MAX);
		}
	}
	WORK();
	return 0;
}